San Francisco 49ers quarterback Colin Kaepernick and a growing number of athletes have been called "unpatriotic" for their refusal to stand during the national anthem. But now, the form of protest may be spreading in the military – an entity where respect to national symbols is expected and such an act holds much more controversy.

Since August, at least two cases have occurred where black members of the military posted public accounts of themselves refusing to stand or salute to the national anthem, an obligation for enlisted troops in the US military that can be enforced by disciplinary actions.

Compared to professional athletes such as Kaepernick, enlisted men or women who choose this form of protest may face more severe consequences and criticism for their actions – and perhaps the reason why they chose to do so in the first place – that could be interpreted as either brave or blatant disrespect for the nation and institution they serve.

In August, an African-American sailor at the Naval Air Technical Training Center in Pensacola, Fla., who has not been identified, posted a video of herself on Facebook sitting down alone on a bench near a flagpole with a raised fist – a symbol for the Black Power movement – while a recording of the national anthem played. It was not a military exercise nor was she in uniform. The video was widely shared by a Facebook page unaffiliated with the US Army that condemned the act.

In the video, the sailor references Kaepernick's protest and explains her actions for freedom of speech and equality, all the while describing her nervousness in doing so and how hard it was, saying it was a "small" but "significant" act.

"I made a small statement and I'm proud of it ... I'm still nervous, my hands are still shaking," she said. "I don't not respect the men and women whom I serve alongside. It's just until this country shows that they got my back as a black woman ... they got my people's back ... I can't and I won't be forced to [stand.]"

A similar protest occurred this month when another sailor with the US Pacific Fleet at Pearl Harbor, Petty Officer 2nd Class Janaye Ervin, posted a status on Facebook about her refusal to stand during the anthem.

"On September 19, 2016, while in uniform, I made the conscious decision to not stand for the Star Spangled Banner because I feel like a hypocrite, singing about 'land of the free' when, I know that only applies to some Americans. I will gladly stand again, when ALL AMERICANS are afforded the same freedom," her now deleted post said, as reported by the Associated Press. "The Navy has decided to punish me for defending the Constitution and has taken away my equipment I need to do my Naval job. It was my pleasure serving my country, I love it dearly, that is why I must do this for you. I will keep you all posted on what happens next!"

Ms. Ervin’s actions elicited reactions from both sides. It triggered Brooklyn resident Brandon Akins to start a Change.org petition called "Keep black soldiers out of jail for choosing not to stand for national anthem," which had the signatures of around 400 supporters at the time of publication. A Facebook page called "Hold Janaye Ervin Accountable," which condemned her for failing to follow navy rules, was also created.

According to the Associated Press, troops have to salute when the anthem is played either to the flag or the direction of the music when they're in uniform. When they're not in uniform, they have to place their hands over their hands or salute.

"If you're driving in your car and you hear the national anthem, you have to stop and get out of your car," Carl W. Baker, a retired Air Force lieutenant colonel, told the Associated Press. It's their first introduction to the military, and a form of respect to the constitution as well as professionalism expected of military members, he said.

Both military members who engaged in the protest received disciplinary actions, although it isn't clear exactly what penalties were imposed. Their cases are still under review.

Dissent in the military is not uncommon. It has precedence in the Mexican-American War, World War I, and Vietnam War, when troops protested against slavery, Jim Crow discrimination, and supported the Black Power movement, as reported by The San Diego Union-Tribune. Especially at a time when many protests against social issues are brewing, such actions can become more common.

"I think it could spread," retired Rear Adm. Donald J. Guter told The San Diego Union-Tribune in an interview about Ervin. "I think that the ideas that this young sailor tried to express are widely felt by others, but the way that she chose to express them becomes the issue."

But political actions – especially controversial ones – can be sensitive topics in the military, especially when members do so in uniform. A recent example occurred in May, when a group of graduating seniors at the United States Military Academy in West Point posed for a picture with raised fists, eliciting concerns about whether they were showing solidarity with the Black Lives Matter movement. The Defense Department bans political activities in uniform.

Sheila Varnado, president of the advisory committee for the African American Military History Museum in Mississippi, told the Associated Press that wearing the uniform "represented not just themselves but the military and the United States," so it "wasn’t appropriate to express personal feelings or protests while in uniform." The video of the first sailor doesn’t show her to be in uniform.

"You're striving for and agreeing with what our country says it wants to be, not necessarily what it is at any given moment in time," she said.

But as The Christian Science Monitor previously reported, not all veterans are against Kaepernick's form of protest and they don't see it as "unpatriotic."

"Part of loving America is being able to say, 'Look, we've got some issues, and I think we need to change some things,'" Army veteran Matt Pelak told the Monitor. "To be brave enough to be willing to stand up on a rooftop and shout it – that's just as patriotic as painting your truck red, white, and blue."